Looking for tracks on the Moon

As a lunar observer, I am repeatedly asked whether the tracks of the six Apollo missions can be seen through a telescope. After all, the descent stages of the lunar modules, three lunar rovers and a lot of scientific equipment were left behind there. Unfortunately, this is impossible even with the largest ground-based telescopes. But on the Internet, it is possible for everyone to go out and explore.

The unmanned US Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon since June 2009. One of the goals of this mission was to identify suitable landing sites for future missions to the Moon. For this reason, the LRO has been photographing the lunar surface in unprecedented detail from an altitude of just 50 kilometres.

The LROC Science Operations Center at Arizona State University is making the images available to the public via an interactive map of the entire lunar surface. Starting from the view of the entire Moon, you can zoom in to any location in the lunar landscape as closely as the resolution of the LRO images permits. So, exciting journeys of discovery through lunar mountains, craters and rilles is now possible.

The six landing sites of the Apollo lunar modules are not just particularly appealing to space travel enthusiasts. Scientists also wanted to see survey images from lunar orbit to accurately determine the locations of soil samples and experiments from the Apollo missions. For the most detailed images, NASA briefly lowered LRO's orbit to 20 kilometres above the lunar surface in August 2011. The images acquired actually show the astronauts' tracks; not every individual footprint, but the trails the astronauts made on the surface and the ruts left by the lunar rovers. The descent stages of the lunar modules, the rovers and scientific equipment show up especially clearly.

So the only question remaining is how the evidence for human activity is found amongst the numerous small craters and other natural surface details, and there are several ways to do this:

'Experts' will try to use known surface features to pick out the landing sites using their own initiative. With Apollo 15, this might be the sharp bend in Hadley Rille at the foot of the Apennine Mountains. The landing site cannot be far from this - after all, the astronauts drove to the rim of the rille while they were there. And, after looking at the image at the highest zoom level, you will find unusual tracks that do not match the Moon’s natural surface. Once you find the site, you will know.

To make searching for the sites easier, I pinpointed all of the Apollo landing sites on a lunar panorama I created with images acquired with my telescope on 16 September 2011. On that day, all the landing sites were on the illuminated side of the Moon.

I had often intensely studied the region around the Hadley Rille in my telescope at a magnification of over 300x. When I 'plunged' into the LRO database to look for the landing site and finally found traces left behind by the astronauts, I realised how incredibly small it all is in comparison to what you usually see through a telescope. So it is no wonder that searching from Earth at even the highest resolution remains fruitless.

There is a shortcut for people who do not want to spend a long time searching; the "Quick map site listing" gives a link marked with [QMAP] for each of the Apollo landing sites, which accurately zooms into the desired location on the LRO map at the highest resolution. The exact location is quickly found if you use the mouse to drag the image from side to side. On the other hand, by zooming out you can quickly see the surroundings of that site.

But the feeling of success is much greater when, after searching for a while, you finally find a landing site on your own. Besides Apollo 15, the easiest to find is Apollo 16, situated between the small but conspicuous North Ray and South Ray craters, and Apollo 17 in the Valley of Taurus-Littrow. The easily visible tracks of the lunar rovers, which were only taken along on these last three missions (J-type) and the striking topography of the landing sites make the task easier. After these preparatory exercises you can try your hand at the more difficult earlier missions. Good luck!

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In 1992, Rolf Hempel started, together with three colleagues, the international ‘Message-Passing Interface’ initiative. The resulting MPI programming model is still the dominant standard in high performance computing. Since 2001 he has been head of the DLR Simulation and Software Technology Facility.
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